Horton

Re: [Patch] ALTER SYSTEM READ ONLY

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Simon Riggs <simon@2ndquadrant.com>
Cc: amul sul <sulamul@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2020-06-18T14:56:27Z
Lists: pgsql-hackers 
On Thu, Jun 18, 2020 at 6:39 AM Simon Riggs <simon@2ndquadrant.com> wrote:
> That doesn't appear to be very graceful. Perhaps objections could be assuaged by having a smoother transition and perhaps not even a full barrier, initially.

Yeah, it's not ideal, though still better than what we have now. What
do you mean by "a smoother transition and perhaps not even a full
barrier"? I think if you want to switch the primary to another machine
and make the old primary into a standby, you really need to arrest WAL
writes completely. It would be better to make existing write
transactions ERROR rather than FATAL, but there are some very
difficult cases there, so I would like to leave that as a possible
later improvement.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Commits

  1. Initialize variable to placate compiler.

  2. StartupXLOG: Don't repeatedly disable/enable local xlog insertion.

  3. StartupXLOG: Call CleanupAfterArchiveRecovery after XLogReportParameters.

  4. Postpone some end-of-recovery operations related to allowing WAL.

  5. Refactor some end-of-recovery code out of StartupXLOG().

  6. Re-enable contrib/bloom's TAP tests.

  7. Remove unnecessary call to ReadCheckpointRecord().

  8. Allow for error or refusal while absorbing a ProcSignalBarrier.

  9. Add comment to explain an unused function parameter

  10. Extend the ProcSignal mechanism to support barriers.

  11. At promotion, don't leave behind a partial segment on the old timeline.